The present invention relates in general to minimizing head off-track in a disk drive and, in particular, to a slider support structure and associated methodology for minimizing off-track due to disk flutter.
A disk drive typically includes multiple disks that rotate on a spindle. Each disk normally has two surfaces for storing data in generally concentric data tracks. The data can be written onto the disk surfaces and read therefrom by transducer heads that are guided over the disk surfaces by an actuator arm. The actuator arm is driven by a voice coil motor controlled by a control system to position the transducer heads relative to the desired data tracks.
The transducer heads are generally mounted on a bottom surface of a support structure commonly referred to as a xe2x80x9csliderxe2x80x9d. This slider, in turn, is typically connected to the actuator arm by way of a suspension load beam and torsion bar flexure. In operation, the torsion bar supports the slider such that the slider is in close proximity to the disk surface for improved data transfer as between a transducer head and an associated data track. In particular, this slider typically xe2x80x9cfliesxe2x80x9d a small distance above the disk surface. This spacing between the slider and disk surface, sometimes referred to as an xe2x80x9cair bearingxe2x80x9d, is maintained by way of interaction between flexural forces of the torsion bar pressing the slider towards the disk surface and hydrodynamic forces incident to travel of the slider over the rotating disk surface. The flexibility of the torsion arm allows the slider to lift off of the disk surface. In addition, the above-noted interaction between the flexural forces and hydrodynamic forces allows the slider to maintain a close spacing relative to the disk surface despite warpage of the disk surface or disk flutter. Such disk flutter may result from various forces including external vibrations and aerodynamic forces associated with turbulence.
Disk flutter results in angular displacements of the disk surface as well as vertical displacements. In order to allow the slider to closely track the disk surface, the slider is generally mounted on a pivot which is attached to the flexural structure. In particular, the slider may be attached to the torsion bar so that it can pivot about an axis generally parallel to the data track axis to allow the slider to roll and about an axis transverse to the data track axis to allow the slider to pitch. Generally, such pivoting is allowed by way of a ball joint or gimbal interface at the top of the slider.
While such support of the slider is generally effective in maintaining a close spacing between the bottom surface of the slider and the disk surface, the pivotal motion of the slider can result in off-track errors, i.e., displacement of a transducer on the bottom surface of the slider relative to the associated data track. As disk drive manufacturers continue to achieve closer spacing of the tracks on the disk surface, the component of off-track error due to disk flutter is becoming a more important consideration. In addition, as the rotating rate of disks is increased, the problem of disk flutter is requiring more attention.
The present invention is directed to structure and associated methodology for minimizing head off-track due to disk flutter. It has been recognized that the head-off-track displacement incident to rolling and pitching of the slider is proportional to the distance between the roll and pitch axes, on the one hand, and the location of the transducer head under consideration on the other. Because sliders have conventionally been supported and pivoted from the top surface of the slider, the above-noted distance has generally included the thickness of the slider as one component. In accordance with the present invention, off-track due to flutter is reduced by configuring the slider support so that a pivot axis or axes are located closer to the transducer head. In addition, a support structure configuration is disclosed that allows the pivot axis or axes to be moved closer to the disk surface without unduly increasing the possibility of disk crashes (i.e., contact between the support structure and the disk surface).
According to one aspect of the present invention, an apparatus for use in reducing transducer head off-track displacement in a disk drive is provided. The apparatus is used in a disk drive wherein a transducer head is carried over a disk surface by an actuator arm. The inventive apparatus includes a slider body for carrying the transducer head, a load beam for use in supportably interconnecting the slider body to the actuator arm, and a gimbal structure for forming an interconnection between the slider body and the load beam. The slider body has a lower surface and an upper surface, where the transducer head is disposed adjacent to the lower surface. The gimbal structure may define first and second pivot axes, where one of the pivot axes allows the slider body to roll relative to the gimbal structure and the other axis allows the slider body to pitch relative to the gimbal structure. The gimbal structure forms the interconnection between the slider body and the load beam such that the slider body is pivotable relative to a first pivot axis that is located between the lower surface of the slider body and the upper surface of the slider body. Preferably, the pivot axis is located closer to the lower surface of the slider body than to the upper surface. In this regard the pivot axis is located a distance from the bottom surface that is preferably no more than ten percent, and more preferably no more than about five percent, of the distance between the lower surface and the upper surface.
In accordance with another aspect of the present invention, a gimbal apparatus is provided for use in interconnecting a slider body to a support structure associated with an actuator arm of a disk drive. The gimbal apparatus includes first structure for forming a first flexible connection to the slider body and second structure for forming a second flexible connection to the slider body. The first connection and second connection are formed on side surfaces of the slider body between an upper surface and a lower surface of the slider body. Preferably, the gimbal structure includes a peripheral portion extending beyond the side surface of the slider body, wherein the peripheral portion is disposed a distance above the bottom surface of the slider body such that the slider body can pivot relative to the gimbal structure without causing contact between the peripheral portion of the gimbal structure and the disk surface. In one embodiment, the gimbal structure includes a first annular ring and a second annular ring peripherally extending about the slider body. The inner ring is flexibly connected to the slider body on left and right sides of the slider body so as to define a first pivot axis. The outer gimbal ring is flexibly connected to the inner gimbal ring adjacent to the front and back sides of the slider body so as to define a second pivot axis. The annular rings thereby allow the slider body to pitch and roll so as to maintain close spacing between a transducer head and the disk surface. Moreover, the configuration of the gimbal structure to define pivot axes between the upper and lower surfaces of the slider body reduces off-track due to disk flutter while having sufficient space to prevent all disk crashes.